fix: replace non-sense error messages on Android

[FlorianFranzen]

Purpose

Noticed some odd error messages in the signer, fixed them to be a lot less confusing.

Scope

Only updates three of the strings used inside the Android app.

[FlorianFranzen]

@Dmitry-Borodin I think it is fairly clear that this is a non-sense message. Anything else you would need for a review?

[FlorianFranzen]

@valentunn @stepanLav @kogeler @antonkhvorov Any update on when maintenance of the repo will be picked up again?

[Dmitry-Borodin]

Oh funny, I can approve, but it does nothing.

[FlorianFranzen]

@Dmitry-Borodin Then what do we have to do that something is done? Was Novasama not awarded treasury funding to continue this project?

[Dmitry-Borodin]

@Dmitry-Borodin Then what do we have to do that something is done? Was Novasama not awarded treasury funding to continue this project?

I don't know, I don't work for Novasama. I think it's better to contact them directly.
This PR seems to be done and just need to be merged.

[FlorianFranzen]

Rebased it and contacted Novasama again in the hope to get this finally merged.

Looks like CI has some permission issues for externally hosted PRs, not much I can do about that.